Investigation of the interactions of incremental surface layer forming and HPPMS coating on fine blanking dies in order to enable a load-applied surface integrity adjustment (TEStOI)

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In the processing of high-strength sheet metal materials for the production of functional components such as brake pad carriers in the automotive industry by means of fine blanking the tool load increases compared to conventional sheet metal materials. Incremental methods for the mechanical surface layer forming, such as deep rolling, are suitable for increasing the tool lifetime by increasing the wear resistance. Mechanical surface treatment is used to improve the surface integrity (OI) of dynamically loaded parts. The OI includes microstructure, hardness profile, residual stresses, surface topography and damage of the tool surface layer. In order to further reduce abrasive and adhesive wear, the functional surfaces of the tools are coated by means of physical vapour deposition (PVD). Using a knowledge-based process design, it is possible to influence the OI of the coating selectively. A specific OI of the coating furthermore has a positive effect on the OI of the tool surface layer and the compound adhesion. In particular, the residual stress and the microstructure of the tool surface layer, however, can be successively relaxed by the thermal stress during the coating deposition as well as under cyclic elasto-mechanical stress of the surface layer during the fine blanking process. The corresponding physical cause-effect relationships with regard to the thermal and elastic stability of the OI are mostly unknown. On the one hand, it is unclear how the heat input during the coating process alters the OI of the tool and what interactions occur between the OI of the coating and the incrementally set OI in the tool. On the other hand, it is unknown how the cyclic elasto-mechanical load during the blanking process affects the OI of the tool surface layer. Therefore, the project is based on the research hypothesis that the OI which has been set by means of incremental surface layer transformation and PVD coating can be designed to be stable in a low-temperature coating process at substrate temperatures T < 300 °C under a friction-induced thermal and subsequent cyclic mechanical load. The thermal and elastic stability of the OI of the tool surface layer as well as the influence of the OI of the PVD coatings are investigated. On the one hand, the OI of the tool surface layer is specifically adjusted and then the tool surface is coated by means of a high-performance plasma process. On the other hand, investigations of the tool surface layer and coatings are carried out in order to analyze the influences of the production processes and to derive a suitable combination of process parameters. In order to expand the findings, the behaviour of the OI is examined in a numerical simulation.